The legacy of forest logging on organic matter inputs and storage in tropical streams

Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear-cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast-growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear-cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest-stream interfaces.     

Phytochemical Characterization of Cannabis sativa L. Roots from Northeastern Brazil

This article describes the phytochemical study of Cannabis sativa roots from northeastern Brazil. The dried plant material was pulverized and subjected to exhaustive maceration with ethanol at room temperature, obtaining the crude ethanolic extract (Cs-EEBR). The volatile compounds were analyzed by gas chromatography coupled with mass spectrometry (GC/MS), which allowed to identify 22 compounds by comparing the linear retention index (LRI), the similarity index (SI) and the fragmentation pattern of the constituents with the literature. By this technique the major compounds identified were: friedelan-3-one and β-sitosterol. In addition, two fractions were obtained from Cs-EEBR by classical column chromatography and preparative thin layer chromatography. These fractions were analyzed by NMR and IR and together with the mass spectrometry data allowed to identify the compounds: epifriedelanol, friedelan-3-one, β-sitosterol and stigmasterol. The study contributed to the phytochemical knowledge of Cannabis sativa, specifically the roots, as there are few reports on the chemical constituents of this part of the plant.     

Study of the Biological Activity and Phenolic Content of the Ethanol Extract of Phyllogonium viride Brid. (Phyllogoniaceae,Bryophyta)

The present study aimed to examine the phenolic content and evaluate the antimicrobial and antioxidant potential of ethanol extracts from the moss species Phyllogonium viride Brid. on the pathogenic bacteria Salmonella enterica serovar enteritidis, Staphylococcus aureus, Listeria monocytogenes and Escherichia coli, and the pathogenic fungi Candida albicans and Cryptococcus neoformans. The antimicrobial activity was determined from Minimum Inhibitory Concentration (MIC) Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC). Antioxidant activity was determined by the DPPH method. Folin-Denis reagent was used for the content of total phenolics and flavonoids and HPLC-DAD for identification of phenolic compounds. The results showed that bacteriostatic and bactericidal activities occurred at concentrations ranging from 9.76 μg/mL–78.13 μg/mL among all evaluated microorganisms. These values, considering the criteria used, suggest the P. viride extract as a potent antimicrobial. For antioxidant activity, P. viride extract was considered weak. Analysis of the phenolic content showed a wide range of compounds, with Kaempferol (0.41 mg/g) being the major compound, followed by t-cinnamic acid and caffeic acid (0.17 mg/g). Although P. viride is a species of moss not yet referenced in scientific publications of biotechnological interest, it has shown promising potential for further studies and possible application as an antimicrobial of natural origin.     

Effects of anti-inflammatory drugs on fever and neutrophilia induced by Clostridium difficile toxin B

This study investigated the ability of Clostridium difficile toxin B, isolated from the VPI 10463 strain, to induce fever and neutrophilia in rats. Intravenous injection of toxin B (0.005-0.5 mug/kg) evoked a dose-dependent increase in body temperature. The febrile response to 0.5 mug/kg of the toxin started in 2.5 h, peaked at 5 h, and subsided fully within 24 h. Toxin B also induced a dosedependent neutrophilia. Pretreatment with indomethacin (2 mg/kg, i.p.) did not affect the neutrophilia induced by toxin B, but significantly reduced the febrile response measured 4 to 8 h after toxin B injection. Dexamethasone (0.5 mg/ kg) also markedly diminished the febrile response induced by toxin B. These results show that Clostridium difficile toxin B induced a febrile response susceptible to inhibition by dexamethasone and indomethacin. Furthermore, they suggest that prostaglandins are not involved in the neutrophilia caused by this toxin.     

Evidence for two possible glnB-type genes in Herbaspirillum seropedicae.

Two glnB-like genes have been isolated from Herbaspirillum seropedicae by complementation of the Klebsiella pneumoniae glnB502 mutant for growth on nitrate. One of these glnB-like genes has been sequenced and shows strong identity with GlnB proteins derived from other organisms. A Tn5-20 mutation of this glnB was Nif negative.     

Comparative Physiology of Dimethyl Sulfide Production by Dimethylsulfoniopropionate Lyase in Pseudomonas doudoroffii and Alcaligenes sp. Strain M3A

Dimethylsulfoniopropionate (DMSP) lyase enzymatically cleaves DMSP, an algal metabolite, to produce acrylate, a proton, and dimethyl sulfide (DMS), the most abundant volatile sulfur compound emitted from oceans. The physiology of DMS production by DMSP lyase was studied in vivo in an Alcaligenes-like organism, strain M3A, a salt marsh bacterial isolate, and in a marine strain, Pseudomonas doudoroffii. Enzymes from both strains were induced at optimum rates by 1 mM DMSP and vigorous aeration. P. doudoroffii was very sensitive to continued aeration and lost activity rapidly; the enzyme was more stable when aeration ceased. In addition to DMSP, acrylate and several of its analogs acted as inducers of DMSP lyase in Alcaligenes sp. strain M3A but not in P. doudoroffii. Turnover of DMSP by P. doudoroffii was enhanced by 3.5% NaCl or seawater, whereas the Alcaligenes sp. strain M3A enzyme was not salt dependent and salt did not greatly affect its activity. The pH profile showed two peaks of DMSP lyase activity (6.5 and 8.8) for Alcaligenes sp. strain M3A and a single peak at pH 8 for P. doudoroffii. Enzyme activity in both organisms was inhibited by methyl-3-mercaptopropionate and homocysteine. Cyanide, azide and p-chloromercuribenzoate inhibited only the P. doudoroffii DMSP lyase. The apparent K(infm) values for DMSP for cell cultures of Alcaligenes sp. strain M3A and P. doudoroffii were ca. 2 mM and <20 (mu)M, respectively. The differences in the physiology of DMSP metabolism in these two bacterial isolates may enable them to exist in diverse ecological niches.     

Neurochemical effects ofl-pyroglutamic acid

The effect ofl-pyroglutamic acid, a metabolite that accumulates in pyroglutamic aciduria, on different neurochemical parameters was investigated in adult male Wistar rats. Glutamate binding, adenylate cyclase activity and G protein coupling to adenylate cyclase were assayed in the presence of the acid.l-pyroglutamic acid decreased Na⁺-dependent and Na⁺-independent glutamate binding Basal and GMP-PNP stimulated adenylate cyclase activity were not affected by the acid. Furthermore, rats received unilateral intrastriatal injections of 10–300 nmol of bufferedl-pyroglutamic acid. Vehicle (0.25 M Tris-Cl, pH 7.35–7.4) was injected into the contralateral striatum. Neurotoxic damage was assessed seven days after the injection by histological examination and by weighing both cerebral hemispheres. No difference in histology or weight could be identified between hemispheres. These results suggest that, although capable of interfering with glutamate binding, pyroglutamate did not cause a major lesion in the present model of neurotoxicity.     

Immunological and genetic characterization of 2-deoxygalactose-resistant, galactokinase-deficient mutants of Chinese hamster cells: evidence for structural mutations at the galK locus.

Ten independent mutants resistant to 2-deoxygalactose and without any detectable galactokinase activity (null-galactokinase mutations) were isolated from mutagenized Chinese hamster somatic cells. They were analyzed for the presence of serologically cross-reacting material (CRM) with antiserum generated against highly purified Chinese hamster galactokinase. All 10 mutants contain cross-reacting material (i.e., were CRM+), indicating that all the mutations affect the correct expression of a product of the galactokinase structural gene. Complementation analysis among them shows that the 10 mutations fall in one functional genetic unit.     

Temperature-dependent morphological changes in membranes of bacillus stearothermophilus

Bacillus stearothermophilus cells vary the lipid fatty acid composition of cytoplasmic membranes with growth temperature. Spin label studies of such membranes have been interpreted to indicate lateral lipid phase separations at the growth temperature. We have now used freeze-fracture electron microscopy to confirm the spin label studies. Freeze-fracture faces of protoplasts indicate slight but distinct protein aggregation at the growth temperature. Aggregation increases rapidly with decreasing quench temperature in wild-type cells. In contrast we were unable to demonstrate extended protein segregation in membranes of a temperature-sensitive mutant that contains more than 58% branched fatty acids. Storage of protoplasts for prolonged times below the lipid phase transition results in the appearance of corrugated fracture faces with 300- to 500-Å repeat patterns, although this organism does not synthesize lecithins.     

Isolation and properties of flagella of trypanosomatids.

A procedufe is described for the isolation of flagella of Crithidia fasciculata, Herpetomonas samuelpessoai and Leishmania tarentolae in a highly purified state and giving reasonably good yield. The 3 types of flagella give a similar electrophoretic pattern of proteins. It is shown that H. samuelpessoai and, to a lesser extent, C. fasciculata flagella confer protection against Trypanosoma cruzi infection.